Structure and rheology of liquid crystal hydroglass formed in aqueous nanocrystalline cellulose suspensions

Abstract

HypothesisLiquid crystal hydroglass (LCH) is a biphasic soft material with flow programmable anisotropy that forms via phase separation in suspensions of charged colloidal rods upon increases in ionic strength. The unique structure and rheology of the LCH gel formed using nanocrystalline cellulose (NCC) is hypothesised to be dependent on colloidal stability that is modulated using specific ion effects arising from Hofmeister phenomena. ExperimentsLCHs are prepared in NCC suspensions in aqueous media containing varying levels of sodium chloride (NaCl) or sodium thiocyanate (NaSCN). The NCC suspensions are characterised using rheology and structural analysis techniques that includes polarised optical microscopy, zeta potential, dynamic light scattering and small-angle X-ray scattering. FindingsThe two salts have a profound effect on the formation process and structure of the LCH. Differences in network density and size of the liquid crystal domains are observed within the LCH for each of the salts, which is associated with the strength of interaction between NCC particles during LCH formation. In comparison to Cl− at the same salinity, the chaotropic nature of the weakly hydrated SCN− enhances colloidal stability by rendering NCC particles more hydrated and repulsive, but this also leads to weaker gel strength of the LCH. The results suggest that salts are a means in which to control the formation, structure and rheology of these anisotropic soft materials.